The FDA, which regulates medical technology, has long opposed large-scale X-ray machine deployment, arguing that people shouldn't be irradiated without a direct medical benefit. So how did 250 X-ray "backscatter" scanners, which potentially increase cancer rates, land in American airports? Because the TSA insists they're safe.

As it turns out, The Food and Drug Administration is only responsible for regulating medical X-ray technology. If the machine isn't designed or designated for medical use, it isn't subject to the FDA's stringent guidelines. Rather, the FDA retains only limited oversight of security scanners with the right to set mandatory safety regulations. Please note, that's "the right" to set mandatory regulations, not "actually did" set mandatory regulations. The FDA instead allows these scanners to operate under voluntary standards determined by a nonprofit group. Currently, 250 X-ray body scanners and 264 millimeter wave scanners, which rely on radio waves and have not been shown to cause cancer, are deployed in airports across the country.

The final say in regulating these machines actually falls under the TSA's jurisdiction—and it doesn't see what all the fuss is about. The Transportation Security Administration has repeatedly asserted that these machines are safe despite widely-held scientific opinion that even modest doses of ionizing radiation can increase one's cancer risk and research suggesting that as many as 100 people a year could contract cancer on account of this exposure—because the amount of radiation emitted from each machine is so small. In its defense, the TSA has supplied research studies supporting this point, though none of them have been published in a peer-reviewed journal. In addition, the TSA argues that backscatter's continued use could help advance scanner technology.

As Robin Kane, the TSA's assistant administrator for security technology, explained to ProPublica,

It's a really, really small amount [of emitted radiation] relative to the security benefit you're going to get. Keeping multiple technologies in play is very worthwhile for the U.S. in getting that cost-effective solution - and being able to increase the capabilities of technology because you keep everyone trying to get the better mousetrap.

The TSA hopes to install one or the other type of scanner in every airport checkpoint by 2014. What's more, the machines are expected to become part of the primary screening process—meaning everybody will have to pass through them, though passengers will be able to request physical pat-downs if they prefer. [ProPublica - Image courtesy of the AP]